Circuit interrupter



VOLTAGE CIRCUIT INTERRUP'I'ER April 5, 1966 Filed June 7, 1963 United States Patent Oflice 3,244,842 CIRCUIT INTERRUPTER Sampei Kameyama, Toshio lto, and Toshimoto Ohkura, Amagasaki-shi,..lapan, assignors to Mitsubishi Denki Kahushiki Kaisha, Tokyo, .lapan, a company of Japan Filed June 7, 1963, Ser. No. 286,328 Claims priority, application Japan, July 30, 1962, 37/312,110 3 Claims. (Cl. 200-144) This invention relates to circuit interrupters'in general and, more particularly, to improved circuit-interrupting structures adaptable for interrupting circuits having relatively high ratesof rise of recovery voltage transient.

A general object of the invention is to provide an improved interrupting device incorporating a pair of serially related circuit breakers having different voltage withstanding characteristics. Preferably, one of said circuit breakers has an immediate extremely high rate of rise of impressed voltage withstanding characteristics, to become thereby immediately effective to prevent reignition of fault conditions having very high rates of rise of recovery voltage transients; and the other serially related circuit breaker has the characteristic of withstanding impressed voltage in the region of the peak amplitude of the recovery voltage transient. Hence, the combined characteristics of both serially related breakers result in eflective and successful interruption of faults of extremely high rates of rise of recovery voltage.

Another object of the present invention is to provide an improved circuit interrupter in which the combined operating characteristics of a vacuum-type circuit interrupter and acompressed-gas circuit interrupter are utilized to the best advantage for minimizing, or substantially preventing restriking of the recovery voltage across the breaker during high rates of rise of the recovery voltage transient, such as produced by kilometric faults.

Still a further object of the present invention is to provide an improved circuit interrupter embodying two different types of circuit-interrupting structures whose voltage withstanding characteristics upon interruption are utilized to the maximum extent.

Additional objects and advantages will readily become apparent upon reading the following specification, taken in conjunction with the drawings, in which:

FIGURE 1 illustrates a graph showing the voltagewithstanding characteristics of different types of circuit interrupters, and the recovery voltage to be encountered during a kilometric fault; and,

FIG. 2 is a circuit-interrupting structure embodying features of the present invention, the contact structure being illustrated in the closed-circuit position.

As electrical power systems are constantly increased in their power capacity, short-circuit currents flowing through them rapidly increase in magnitude, and the socalled kilometric faults have become such as to impose very severe requirements upon air, or gas-blast circuit interrupters. The reason for this is that the air-blast circuit interrupter has a so-called insulation-recovery characteristic, such as illustrated by the reference numeral 1 in FIG. 1, whereas in any kilometric fault, a restriking voltage having a wave form, such as shown by curve 2 in FIG. 1, appears immediately after interruption at the current zero as a result of super-imposing upon the restriking voltage a high-frequency oscillation caused by a reciprocal reflection along the line. This leads generally to failure of the interrupting units of the prior art.

To solve the foregoing problem, circuit interrupters have recently been manufactured having a complicated structure and including three interrupting points, two of 3,244,842 Patented Apr. 5, 1966 which include inserted thereinlow resistances for suppressingv the impressed voltages.

The present invention contemplates the elimination of the aforementioned disadvantages of conventional air-blast or gas-blast circuit interrupters by utilizing the special insulating characteristics of a vacuum switch. Any vacuum switch has a high resistance to both the slope of a current flowing therethrough, and a rapidly risinginsula- .tion rate for a restriking voltage (rate of rise of recovery voltage) across the same'near to the current zero interruption point, which imposes severe requirements upon a conventional type of air-blast circuit interrupter. Taking, as an example, a small vacuum switch including tungsten electrodes, experiments have proved that the same withstands a current slope of 10 amperes/microsecond and a voltage rate of rise of 20 kv./microsecond or more. However, such a vacuum switch has the disadvantage that it is inferior to an air-blast circuit interrupter in the range of the peak of the restriking voltage. The insulation recovery characteristics of a vacuum switch may be represented by the curve 4 in FIG. 1.

As a result, the present invention contemplates the provision of a circuit interrupter of high interrupting performance comprising a high-pressure circuit interrupter, such as an air-blast circuit interrupter, and a vacuum switch connected in series thereto, whereby the vacuum switch bears a high rate at which a restriking voltage is imposed immediately after a current interruption, whereas the high-pressure circuit interrupter resists the peak amplitude of the restriking voltage.

With reference to FIG. 2 of the drawings, it will be apparent that there is provided a vacuum switch 5 disposed in series relation with an air, or gas-blast type of circuit interrupting structure 6. The vacuum switch 5 comprises a stationary contact 7, a movable contact 9, the latter entering the evacuated envelope 10 through means of a Sylphon bellows 11. The extension 12 of the movable contact 9 is biased by a spring 14 to the open-circuit position. As shown, the accelerating spring 14 has a spring seat, a flange portion 15 fixedly secured to and movable with the operating rod portion 12 of the movable contact 9. The movable contact as shown, is latched in the closed-circuit position by a latching device 15, which may be electrically released in a manner hereinafter described.

To effect closing of the vacuum circuit interrupter 5, pressure may be fed to an operating cylinder 16, within which reciprocally moves a piston 17 attached to the lower extremity of the operating rod 12.

A line connection L is secured to an upper conducting plate 20, to which the upper relatively stationary electrode 7 is affixed. The circuit extends by way of a sliding connection 22 to a terminal 24 or" the gas-blast breaker 6.

The gas-blast breaker 6, as shown, comprises a nozzleshaped stationary contact 28, and a movable rod-shaped contact 259, which is actuated during the opening opera tion by the opening of a blast valve 30. The blast valve 3%, in turn, is electrically actuated by a solenoid device 31, which, as shown, is responsive either to the pressing of an open button, or to a relay 38 responsive to a current transformer 40' monitoring the current conditions in the line L To eifect closure of the compressed-gas circuit interrupter 6 as well as closure of the vacuum switch 5, a suitable closing valve 4t? is provided, which controls the admission of air from the reservoir 45 to the opera-ting cylinders 16, 46 to effect closing movement of the respective pistons 17, 49 therein. Closing movement of the piston 49 within the operating cylinder 46 of the compressed-gas breaker 6 is effective through the linkage 50 to force the movable rod-shaped contact 29 toward its closed-circuit position, as shown in FIG. 2.

It will be apparent from the foregoing description of the circuit interrupter of FIG. 2 that when an opening signal is fed to the device, the vacuum switch 5 and the high-pressure circuit interrupter 6 are opened at the same time, so that the characteristic of the circuitinterrupting device, as a whole, is that of each of the individual interrupters 5, 6 in combination, so that a resulting voltagewithstanding curve, such as indicated by the reference numeral 60 in FIG. 1, is the result.

It will be apparent that by combining the characteristics of the individual breakers 5, 6, as indicated by the reference numeral 60 of FIG. 1, interruption may be successfully achieved even though high rates of rise of recovery voltage during fault conditions are encountered.

As Well known by those skilled in the art, a kilometric fault condition is encountered when the fault occurs relatively closely to the circuit interrupter under consideration, and, for many instances, this is considered to be one-half mile by those skilled in the art. The result is a very high rate of rise of recovery voltage imposed upon the breaker.

From the foregoing description of the invention, it will be apparent that there is provided an improved circuitinterrupting structure comprising a vacuum switch 5 in series with a cooperating gas-blast breaker 6, the combined voltage-withstanding characteristics of both breakers having the result, such as illustrated by the curve 60 in FIG. 1. By such a combination, high rates of rise of the recovery voltage may be withstood and successful interruptions achieved.

Although there has been illustrated and described a specific structure, it is to be clearly understood that the same was merely for the purpose of illustration and that changes and modifications may readily be made therein by those skilled in the art without departing from the spirit and scope of the invention.

We claim as our invention:

1. A circuit interrupting arrangement for interrupting relatively high rates of rise of recovery voltage comprising, in combination, a vacuum-type circuit interrupter having a high rate of rise of voltage withstanding characteristic, another circuit interrupter having the characteristic of withstanding impressed voltage in the region of peak amplitude of the recovery voltage transient, means for electrically connecting the two circuit interrupters in series to achieve their combined voltage-withstanding characteristics, and means for elfecting substantially simultaneous contact opening movement of both circuit interrupters during circuit interruption.

2. A circuit interrupting arrangement for interrupting relatively high rates of rise of recovery voltage comprising, in combination, a vacuum-type circuit interrupter having a high rate of rise of voltage withstanding characteristic, a serally-related gas-blast circuit interrupter having the characteristic of withstanding impressed voltage in the region of peak amplitude of the recovery voltage transient, means for electrically connecting the two circuit interrupters in series to achieve their combined voltagewithstanding characteristics, and means for effecting substantially simultaneous contact opening movement of both circuit interrupters during circuit interrupton.

3. The combination according to claim 2, wherein means are provided to effect the simultaneous closing operation of both serially-related circuit interrupters.

References Cited by the Examiner UNITED STATES PATENTS 2,859,309 11/1958 Schwager et a1. 200-144 X 2,970,198 1/1961 Schrameck 2O0145 X FOREIGN PATENTS 409,963 5/1934 Great Britain.

KATHLEEN H. CLAFFY, Primary Examiner.

BERNARD A. GILHEANY, Examiner.

P. E. CRAWFORD, Assistant Examiner. 

1. A CIRCUIT INTERRUPTING ARRANGEMENT FOR INTERRUPTING RELATIVELY HIGH RATES OF RISE OF RECOVERY VOLTAGE COMPRISING, IN COMBINATION, A VACUUM-TYPE CIRCUIT INTERRUPTER HAVING A HIGH RATE OF RISE OF VOLTAGE WITHSTANDING CHARACTERISTIC, ANOTHER CIRCUIT INTERRUPTER HAVING THE CHARACTERISTIC OF WITHSTANDING IMPRESSED VOLTAGE IN THE REGION OF PEAK AMPLITUDE OF THE RECOVERY VOLTAGE TRANSIENT, MEANS FOR ELECTRICALLY CONNECTING THE TWO CIRCUIT INTERRUPTERS IN SERIES TO ACHIEVE THEIR COMBINED VOLTAGE-WITHSTANDING CHARACTERISTICS, AND MEANS FOR EFFECTING SUBSTANTIALLY SIMULTANEOUS CONTACT OPENING MOVEMENT OF BOTH CIRCUIT INTERRUPTERS DURING CIRCUIT INTERRUPTION. 